JPH04148046A - Car speed sensor failure deciding device - Google Patents

Abstract

PURPOSE:To prevent wrong diagnosis of a car speed sensor regardless of whether on a horizontal road or a steep uphill road, and to improve failure detecting ability of the car speed sensor on a flat land, by prohibiting the failure deciding of the car speed sensor by a prohibiting means when the inclination angle of the vehicle comes to a specific value or more. CONSTITUTION:In a car speed sensor failure deciding device, a failure of a car speed sensor 103 is decided by a deciding means 101 when a vehicle is decided to be in a specific condition depending on the output signals from the car speed sensor 103 and detector group 104, and the like. In this case, when the inclination angle of the vehicle is at a specific value or more depending on an inclination angle detecting means 102, the deciding means 101 is given an instruction to prohibit the failure decision by a prohibiting means 105. As a result, wrong detection is prevented securely, and the deciding value of the engine rotation frequency can be reduced even to a steep uphill road.

Description

[Detailed Description of the Invention] [Summary] The present invention provides a vehicle speed control system having a determination means for determining whether or not the vehicle speed sensor is malfunctioning based on a vehicle speed sensor and a group of detectors that detect each state of the vehicle. Regarding the Sansa failure determination device, the vehicle speed sensor failure detection ability of the determination means is improved by further providing an inclination angle detection means and a prohibition means for prohibiting failure determination when the inclination angle of the vehicle exceeds a predetermined value. This is what I did.

[Industrial application field]

The present invention relates to a vehicle speed sensor failure determination device that suitably performs failure determination of a vehicle speed sensor.

[Conventional technology]

The electronic fuel injection control device uses, for example, a microcomputer to suitably control the fuel injection amount, ignition timing, idling speed, etc. based on signals from various sensors indicating the state of the engine.

Such an electronic fuel injection control device is provided with a self-diagnosis function (hereinafter referred to as a vehicle speed sensor fail diagnosis function) for diagnosing a failure of a vehicle speed sensor or the like.

The vehicle speed safety failure diagnosis function is executed by a microcomputer program installed in the electronic fuel injection control device, and determines whether the vehicle speed sensor is malfunctioning based on signals from the vehicle speed sensor and a group of sensors that detect each state of the vehicle. It is to judge whether or not. If it is determined that there is a malfunction, the malfunction is stored in the memory in the microcomputer, or a warning lamp in the vehicle is turned on to warn the driver of the abnormality.

This vehicle speed sensor fail diagnosis function basically determines that the vehicle speed sensor is malfunctioning when the vehicle speed read from the vehicle speed sensor becomes 0 while the vehicle is running. In other words, the engine speed is the determination value (for example, 1500 rpm)
With the above, for example, if the shift is set to D range,
It is determined that the vehicle is running, and if the signal from the vehicle speed sensor is O at this time, it is determined that the vehicle speed sensor is malfunctioning. Further, it is preferable that the determination value of the engine rotational speed at this time is set to a rotational speed that is equal to or higher than the idle rotational speed of the vehicle and as low as possible.

This is because the vehicle speed sensor fail diagnosis function does not determine that the vehicle speed sensor is malfunctioning unless the second engine rotational speed exceeds the determination value. Therefore, the lower this determination value is, the more the failure detection ability of the vehicle speed sensor fail diagnosis function improves.

However, if the determination value is low, the vehicle speed sensor fail diagnosis function will erroneously detect that the vehicle speed sensor is malfunctioning even though the vehicle speed sensor is normal in a state like the one shown below. That is, (1) Stop the vehicle, set the foot brake to the D range while fully depressing it, and depress the accelerator pedal. (The engine speed increases to approximately 200 Orpm.) In other words, if the judgment value is set to a low value of 150 Orpm, the output of the vehicle speed sensor is 0 because the vehicle is actually stopped, but the engine speed increases to, for example, 200 Orpm. Since the vehicle has risen to 300 degrees, it is determined that the vehicle is moving and the above-mentioned false detection occurs.In order to more reliably prevent false detection, the stop lamp detector is turned on by looking at the output of the existing stop lamp detector. That is, if the foot brake is depressed, failure diagnosis in the state shown in (■) is prohibited. Therefore, by including the state of the stop lamp detector as a judgment condition, it is possible to detect a state such as (2), so that the above-mentioned judgment value can be set low and erroneous judgments can be prevented.

However, with this vehicle speed sensor failure determination device, the above-mentioned erroneous detection occurs in the following situation (2).

That is, (1) the vehicle is driven at extremely low speed (vehicle speed less than approximately 31/h) on a steep road.

Such a situation occurs, for example, when the driver encounters a traffic jam on the road and is driving slowly.

In this state, the engine speed exceeds the determination value of 1500 rpm, so it is determined that the vehicle is running, but the actual vehicle speed is extremely low, so the microcomputer may regard it as 0. Therefore, the above-mentioned erroneous detection will occur.

Therefore, in order to prevent false detection due to this state,
The determination value for vehicle speed sensor failure determination was set to a relatively high value of 2500 rpm, for example.

[Problem to be solved by the invention]

However, as mentioned above, when the engine speed judgment value is set high, the detection ability of the vehicle speed sensor fail-dagu decreases.Therefore, in the past, the detection ability had to be sacrificed to prevent false detection. There wasn't.

[Means to solve the problem]

In order to achieve the above object, the present invention includes: a vehicle speed sensor 103; a detector group 104 that detects each state of the vehicle; and a determination that determines a failure of the vehicle speed sensor 103 using the vehicle speed sensor 103 and the detector group 104. A vehicle speed sensor failure determination device comprising: a tilt angle detection means 102 for detecting the tilt angle of the vehicle; and based on the tilt angle detection means 102, the failure determination is made when the vehicle tilt angle is equal to or greater than a predetermined value. Prohibited means 105
A vehicle speed sensor failure determination device is characterized in that it is provided with the following.

[For production]

When the determining means 101 determines that the vehicle is in a certain state based on the output signals from the vehicle speed sensor 103 and the detector group 104, the vehicle speed sensor 103 is in a state where it can be determined to be faulty. At this time, the prohibiting means 105 causes the determining means 105 to prohibit the failure determination based on the inclination angle detecting means 102 if the inclination angle of the vehicle is equal to or greater than a predetermined value.
01. That is, the determining means 101 prohibits failure diagnosis of the vehicle speed sensor 103 when the road becomes steep.

Therefore, since the condition of the climbing road can be detected, erroneous detection can be reliably prevented even in the case of a steep climbing road, and the determination value of the engine rotation speed can be lowered.

[Embodiments of the invention]

FIG. 2 is a block diagram showing one embodiment of the present invention.

A processing circuit 1 within the electronic fuel injection control device is composed of an A/D converter 7, an input interface 8, a microcomputer 9, and an output interface 10. Then, based on the signals from the crank angle sensor 4 and other sensors not shown in the map, the fuel injection amount, ignition timing, target idle speed, etc. are calculated, and the corresponding output signals are shown in the diagram from the output interface 10. The signal is sent to an actuator, etc. The processing circuit 1 also has a vehicle speed sensor fail diagnosis function for diagnosing a failure of the vehicle speed sensor 3.

The vehicle speed sensor 3 detects the speed of the vehicle, and its detection signal is input to the input interface 8. Further, a signal for detecting the rotational speed of an engine (not shown) is inputted to the input interface 8 from a crank angle sensor 4 (not shown).

The neutral signal detector detects whether the shift position in the vehicle is in the neutral range or not, and sends a signal indicating this to the input interface 8.

The stop lamp signal detector detects the braking state of the vehicle, that is, whether or not the brake is depressed, and sends a signal indicating this to the input interface 8.

As described above, the signal input to the input interface 8 is shaped into a pulse signal, etc., and then sent to the microcomputer 9.
is input. Further, the detection signal of the inclination sensor 2 that detects the inclination angle of the vehicle, that is, the condition of the climbing road, is sent to the A/D converter 7.
After being converted into a digital signal by the microcomputer 9, the signal is input to the microcomputer 9.

The microcomputer 9 performs calculations, judgments, memories, etc. based on the above-mentioned detection signals, and the microcomputer 9 includes a judgment means and a prohibition means.

The microcomputer 9 diagnoses whether the vehicle speed sensor 3 is malfunctioning based on the vehicle speed, engine speed, neutral signal, stop lamp signal, and vehicle inclination angle.

The above program operation of the microcomputer 9 will be explained in detail. FIG. 3 is a flowchart for explaining the program operation of the microcomputer 9 in this embodiment, and shows a portion of vehicle speed sensor fail diagnosis.

First, step S1 is for determining whether the vehicle speed is approximately O or not. If the vehicle speed is less than 3klI/h, the process proceeds to step S2, where the engine rotation speed NE detected by the crank angle sensor 4 is determined. value i.e. 1500 rpm
Determine whether or not the above is true. If the speed is 1500 rpm or more, the process proceeds to the next step S3. In step S3, the neutral signal detector 5 determines whether the neutral switch is off, that is, the shift is set to the D range, etc., and if it is set, step S4 Proceed to.

That is, step S2. S3 is to judge whether the vehicle is running or not. If YES in step S3, step S1 indicates that the vehicle speed is almost 0, but steps S2 and 33 indicate that the vehicle is running normally. It is determined that there is a high possibility that the vehicle speed sensor 3 is malfunctioning. Further, if the vehicle speed is 3 km/h or more in step S1, the vehicle speed sensor 3 is considered to be normal, a counter to be described later is reset in step S8, and it is determined to be normal in step SIO. And step S2. Either one is N in S3
If O, it is assumed that there is a strong possibility that the vehicle is in a normal stopped state (idle state), and the process proceeds to step s7, where step S
Similarly to 8, the counter is reset and the failure diagnosis of the vehicle speed sensor 3 is not performed in step S9.

Next, in step S4, the stop lamp detector 6 determines whether or not the foot brake etc. is being depressed. It is determined that the brake or the like is depressed, the vehicle is in the D range, and the accelerator pedal is depressed, and the vehicle speed sensor 3 is considered not to be malfunctioning, the counter is reset in step S7, and the process proceeds to step S9, where no malfunction diagnosis is performed. That is, step S4 prevents erroneous detection resulting in the state shown in (2). However, if the foot brake or the like is not depressed in step S4, it is determined that there is a higher possibility that the vehicle speed sensor 3 is malfunctioning, and the process proceeds to step S5, where the inclination angle of the vehicle has reached a predetermined angle (for example, 20
') or more. YES in this step S5
If so, it is determined that the situation is as shown in ■, that is, a state where the vehicle is running at an extremely low speed on a steep uphill road, and the process proceeds to step S7.

Further, if it is determined in step S5 that the inclination angle is 20 degrees or less and the road is not steep, that is, if the vehicle is not in the state shown in (■), it is determined that the vehicle speed sensor 3 is in a failure state, and the process proceeds to step S6. In step S6, it is determined whether the failure state of the vehicle speed sensor 3 continues for a predetermined period of time. In this case, the counting operation of the counter starts when the process moves from step S5 to step S6 for the first time. Then, until 8 seconds have passed, the process moves from step S6 to step S9 and no determination is made, and step S7. If 8 seconds pass without being reset in S8, an abnormality is determined in step Sll, that is, it is determined for the first time that the vehicle speed sensor 3 is malfunctioning, and the RA
Store it in memory such as M.

As described above, step S5 can prevent erroneous detection due to the situation like ■, and the vehicle speed sensor failure determination device can detect not only the situation like ■ but also the situation like ■. Therefore, there is no need to increase the determination value for the situation like ■, and the determination value can be set as low as 150 Qrpm, as shown in step S2 in FIG.

〔Effect of the invention〕

As described above, according to the present invention, the prohibition means prohibits the failure determination of the vehicle speed sensor when the tilt angle of the vehicle exceeds a predetermined value. Misdiagnosis can be prevented reliably, and the failure detection ability of the vehicle speed sensor on flat ground can be improved.

[Brief explanation of drawings]

FIG. 1 is a principle diagram for explaining the present invention, FIG. 2 is a block diagram showing an embodiment of the present invention, and FIG. 3 is a flow chart for explaining the operation of a microcomputer in the embodiment of the present invention. be. In the figure, 101: determination means, 102: tilt angle detection means, 1
03: Vehicle speed sensor, 104: Detector group, 105: Inhibiting means, 9: Microcomputer.

Claims (1)

[Scope of Claims] A vehicle speed sensor failure determination device comprising: a vehicle speed sensor; a group of detectors for detecting each state of the vehicle; and determining means for determining failure of the vehicle speed sensor using the vehicle speed sensor and the group of detectors. , characterized in that it is provided with a tilt angle detecting means for detecting the tilt angle of the vehicle, and a prohibiting means for prohibiting the failure determination when the tilt angle of the vehicle is equal to or greater than a predetermined value based on the tilt angle detecting means. Vehicle speed sensor failure determination device.